The forces responsible for stretching a muscle can broadly be categorized into active stretching and passive stretching. Passive stretching refers to when outside forces assist in the stretching process; these extra forces contribute to muscular and fascial elongation. Examples include gravity, momentum, force applied by another person, or force applied by the indivdual, as in pulling on the feet to get a deeper hamstring stretch.
- Brookes, Douglas S. (2004). The Complete Book of Personal Training. Champaign, IL: Human Kinetics.